Effects On The Growth And Tillering Of Water Hyacinth At Different Nitrogen And Phosphorus Levels And The Basis For Scientific Salvage

Water hyacinth (Eichhornia crassipes (Mart.) Solms), an aquatic plant native toSouth America, is now widely distributed all over the world and has become one of themost malignant weeds in the world. In recent years, because of the environmentalpollution and water eutrophication, water hyacinth has multiplied and occupied thesurface of water. This has changed the water environment resulting in the death of manyliving beings and destroyed the structure of aquatic ecosystem. The invasion of waterhyacinth has caused serious social, economic and environmental problems with itscapacity of fast growth and reproduction. The growth of water hyacinth is influenced bya variety of environmental factors. Therefore, in this study we started from two aspectsof the indoor simulation and field cultivation of water hyacinth. By studying the effectsof different environmental factors on the growth and reproduction of water hyacinth,such as N, P, temperature, light intensity and so on. We try to find out the right nutritioncondition for growth, the reason of overgrowth and the best means and time to salvagewater hyacinth scientifically. The purpose is to provide a scientific base for the controlof water hyacinth and the monitoring of sensitive areas. The results showed that:Within the concentration range of this experiment, the combination of which the Nconcentration was4.5mg/L and P was0.9mg/L was the optimal nutrients needed forgrowth of water hyacinth, and the fittest ratio of N and P for growth was7:1. Thecombination of which the N concentration was4mg/L and P was0.8mg/L was theoptimal nutrients needed for tillering of water hyacinth, and the fittest ratio of N and Pfor tillering was1:7. We will make the salvage and retaining of water hyacinth combined to establish a region-specific salvage in the most sensitive areas where thenitrogen and phosphorus concentration in accord with the optimum conditions.The IAA/(ZR+Z) ratio was inversely related to tiller number. The higher wasnutrient concentration in certain concentration range, the lower was IAA/(ZR+Z) andthe higher was tillering number; compared with Nitrogen, phosphorus in the nutrientsolution played more important role in the tillering of water hyacinth.The increase of temperature and light would accelerate the growth rate of the waterhyacinth which has obvious Seasonal Characteristic in different months and it alsopromoted the tillering. Large-scale growth of water hyacinth may be related to the initialpopulation density. The smaller was the initial population density from10%to50%, themore be weight gain and the faster was the growth of water hyacinth.Based on the results and natural condition of Su Zhou, the following principlesshould be followed for the control and rational use of water hyacinth.(1) Without affecting the normal passage of the river, we can retain the smalldensity of water hyacinth in a certain area of the river with nets to absorb nitrogen andphosphorus for purifying the water.(2) The rational time to salvage the water hyacinths effectively is from March toJune every year.(3) Nets should be placed at the intersection of the waters in rainy season of Juneto prevent the water hyacinth floating around with the river or rain. Water hyacinthsexpand their living areas in this way, and we should stop it to avoid other watersaffected.(4) Humans should reduce the emission of pollution sources which is the key tocontrol the overgrowth of water hyacinth.